ResourceLoader loads user CSS and MediaWiki:Common.css 3 times.
Example source code of the head ouput:
<head>
<meta charset="utf-8" />
<title>Upload file - MixesDB</title>
<meta name="robots" content="noindex,nofollow" />
<link rel="shortcut icon" href="http://www.mixesdb.com/favicon.ico" />
<link rel="search" type="application/opensearchdescription+xml" href="/db17/opensearch_desc.php" title="MixesDB (en)" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=mediawiki.legacy.commonPrint&only=styles&skin=monobook&*" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=mediawiki.legacy.shared&only=styles&skin=monobook&*" />
<link rel="stylesheet" href="/db17/skins/monobook/main.css?301" media="screen" />
<!--[if lt IE 5.5000]><link rel="stylesheet" href="/db17/skins/monobook/IE50Fixes.css?301" media="screen" /><![endif]-->
<!--[if IE 5.5000]><link rel="stylesheet" href="/db17/skins/monobook/IE55Fixes.css?301" media="screen" /><![endif]-->
<!--[if IE 6]><link rel="stylesheet" href="/db17/skins/monobook/IE60Fixes.css?301" media="screen" /><![endif]-->
<!--[if IE 7]><link rel="stylesheet" href="/db17/skins/monobook/IE70Fixes.css?301" media="screen" /><![endif]--><meta name="ResourceLoaderDynamicStyles" content="" /><link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=site&only=styles&skin=monobook&*" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=user&only=styles&skin=monobook&user=MDB&version=20110702T150017Z&*" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=site&only=styles&skin=monobook&*" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=user&only=styles&skin=monobook&user=MDB&version=20110702T150017Z&*" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=site&only=styles&skin=monobook&*" />
<link rel="stylesheet" href="/db17/load.php?debug=true&lang=en&modules=user&only=styles&skin=monobook&user=MDB&version=20110702T150017Z&*" />
</head>
Version: 1.17.x
Severity: enhancement
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=61577